Metal oxide particles mainly serve as adsorbents, catalysts, and electrode materials of a battery and a capacitor in a wide range of applications.
Specifically, the surface area of porous metal oxide particles is significantly larger than that of a bulk particle, showing an advantage of significantly increased reactivity in electrical and chemical applications. As such, porous nanomaterials have been applied in a large number of industrial fields including separation, adsorption, catalysis, etc., depending on the structure and size of their unique pores. Specifically, nanomaterials including iron oxide and metal such as nickel, cobalt, etc. are magnetic at room temperature, and thus can be used in magnetic separation and drug delivery. Also, porous metal oxide materials made based on transition metals and oxygen have been obtained by using polymer surfactants or any material that can be easily eliminated by hydrofluoric acid, such as silica, as a template. However, these methods generally do not allow uniform control of the size of the pores.
Porous metal oxide particles have been obtained by various synthesis methods such as chemical vapor deposition (CVD) or solvothermal synthesis.
There has been another method for preparing a porous metal oxide body which has been known, that uses polymer materials or silica materials, in which the shape has been already formed, as a template to impregnate metal salts, and then removes the materials used as the template by thermal or chemical treatments.
Recently, as an alternative method, a technique that is capable of obtaining porous particles of transition metals by carrying out thermal decomposition from particles of metal oxalate compounds has been reported. When metal oxalate hydrates are heated to a high temperature of 300° C. or greater, the carbon atoms that formed the crystals in the metal oxalate are eliminated as either carbon monoxide or carbon dioxide, and at the same time, many pores are formed. Therefore, metal oxalate hydrates can be used as a key precursor in forming various metal oxide particles (Teramae et al. Langmuir 2013, 29, 4404; Donsheng Yan et al., Adv. Funct, 2008, 18, 1544; Korean Patent No. 10-1198489).
The metal oxalate materials can be diversely synthesized depending on the characteristics of each metal used. A generally known method involves a chemical reaction of a metal precursor with oxalic acid to obtain the metal oxalate materials (Korean Patent No. 10-0555400).
However, the method for obtaining the metal oxalate materials by reacting these metal precursors with oxalic acid showed limitations in controlling the shape of particles, as well as the size of particles.